'Free will' in the Bible

There you shall bring your burnt offerings, your sacrifices, your tithes, the contribution of your hand, your votive offerings, your freewill offerings, and the firstborn of your herd and of your flock.

You are not allowed to eat within your gates the tithe of your grain or new wine or oil, or the firstborn of your herd or flock, or any of your votive offerings which you vow, or your freewill offerings, or the contribution of your hand.

Then you shall celebrate the Feast of Weeks to the Lord your God with a tribute of a freewill offering of your hand, which you shall give just as the Lord your God blesses you;